Alkylation of hydrocarbons



i United States fatent O 'This investies relates tp the airy-lation ef ,stefanie hye drocarbons with monolkyl Vhefn'zenes, and -more speci cally relates to the alkylationof certain mononuclear aromatic hydrocarbons' with monoalkyl benz'eries having atleast 2 carbon atoms in the alkyl group.

One speciiic'eriibodinient of they inyention relates to a process for producing adarylall'anel hydrocarbon `which comprises i"`eactirg` under specific cnditifls', as hereinafter defined, a mononuclear aromatichydrocarbon, such as ben-zene, with a monoalltylbenzenehaving at least' two carbor'iv atoms kinA lthe allyl substituent, such as'V ethylbenzene, by subjecting a' mixture thereof to the action of a tertiary olefin and hydrogen fluoride. It has been found that under these conditions'v ythe niorioalkyl benzene e alkylatesythe mononuclear' varomatic to form a diarylalkane y hydrocarbon, and that`alltyl'atiorl'r of either vrorriatie 're` actant with the tertiary olefin is not observed to any sub-v stantial extent.

In order to illustrate the processof the invention, isobutylene is added to an admixture of benzene, ethylbenzene, and hydrogen fluoride while maintaining the temperature et the' reaction inixturewitliiti the range of frein 100 C. te 185 C. Thereaetipnpreduet of benzene and cthylbenzene, 1,1-diphenylethane, isfformed and can be recovered from the Areaction mixture by distillation. Under optimum conditionsuof reaction, substantially' rio tertiary' but'ylbenzene er 'tertiary biitylethylbeszene is eb'- setved. This reaction' isjillust'ratetl by tbe following equation: i

@einem (onine-leoni Y ln mycopending patent applicatiomSy'erial No. 381,752, tiled September 22, 1953, the dimerization of mono nuclear aromatic hydrocarbons, such as ethylbenzene,

from l to 20 'carbov'nvatorns and wherein R1 is an alkyl radicalr or .a cycloalkyl radical havingfrom l to 20 carbon atoms, or a hydrogen atom. Thealkyl benzene thus has atleast two carbon atomsinthevalkyl group and at least one hydrogen atom is attachedf-to the carbon atom of the alkyl group which is joined to the" aromatic nucleus.

Ethylbenzene and cunieiie' (isopropylben'zene) are prev ferred reactants in therv present process; Other monoalkyl benzenes which may be employed include, for example,

n-propylbenz'ene, secondary bu'tybenzene, secondary amylbenz'e'ne, phenylcyclohexylmethane, l-phenyl-Z-cyclohexyletllane and the like; Ihemonoalkyl benzene reactant is preferably substantially free of other hydrocarbons, and best results are obtained when the presence of other hydrocarbons is maintained below 10%. ,Howeven hydrocarbons which do not reactrude'r the conditions employed, Vsuch as normal parans, may be present to an extent of about 40% Without', adversely affecting the reaction. lsoparahns react under the conditions employed in the process, and hence they should not. be present to an `appreciable extent.

By tertiary oleiins, as used herein, is meant ahydrocarbon having an oleinic double bond and at least one tertiary carbon atom. It is preferred to employ a tertiary olefin wherein the branched chainlis attached to theuunsaturated carbon atom. Tertiary oleiins which give lgood results include, vv for example, irsobutylene, Zemethylbu# tene-2; 2=methylbutene1; 2-x`nethy'lpentene-2; 3-etl1'ylpe`ntene-2; l-rnethy'lcyclohexene; 4 methylcyclohexene;and

` is preferablymaintained within the range of from 0.1:1

to 1:1. Where thev mole `ratio is about 0.1,:1, a relatively v f high yield of the diarylalkane based on conversion is obtained, while at higher'mole vratios a higher total conversion is obtained.` The quantity of hydrogen fluoride to employ is not critical but is advantageously maintained in excess. e Y olen of from 1:1 tti-20:1 is suitable.

lit is preferred to employ an excess of the mononuclear aromatic hydrocarbon. A nioleY ratio of mononuclear aro'- at least 'as' high as 100 C; At temperatures of below 100 below 100 C.

under the influence of a tertiary olen andvhydrogen lluoride is described. In the presence of benzene and under the reaction conditions herein defined, the dimerization reaction of Serial No. 381,752 is 'substantially completely suppressed so that the dimer of the monoalkyl aromatic in the present'process does not constitute a product of the reaction.

Benzene is the preferred mononuclear aromatic hydrocarbon to employ. The benzene nucleus may be substituted with from 1 to 4 methylY groups and good results obtained therewith, for example, toluene, the xylenes, and the trimethyl benzenes, such as mesitylene, give good results.

Monoalkyl benzenes which can be employed in the process of the invention have the formula il? e @i C., alkylation of the monoalkyl aromatic by the tertiary 'olefin is' substa-ltillyA the only reaction obtained, although disproportion is also observed at temperatures only'slightly It is preferred to employ temperatures below 185 C. since athighe'r temperatures a wide variety of products is obtained due". to reactions of the product under the influence of a catalyst. Accordingly, it is essential that the temperature of reaction be maintained at least as high as C. and preferably is maintained at a temperature of not above C. The pressure to employ is not critical so long as reaction is-maintained in the liquid phase. In general the pressure will vary from atmospheric up to about 500 p. s. i. Time is also not considered a critical Variable, it being apparent that sufiicient time should be allowed to obtain a substantial yield of,

the desired product. The usual time of reaction will be from 10 minutes to about 5 hours. v

In carrying out the process of the invention, the tertiary olefin and hydrogen fluoride should not be contacted except in the presence of both the monoalkyl benzene land the mononuclear aromatic. A preferred method of performing the process is to admix the monoalkyl benzene and the mononuclear aromatic with hydrogen uoride, and to then add tertiary olefin, with agitation, to the mixture.

A mole'ratio of hydrogen fluoride to tertiary As above described, patent application Serial No. 381,752 describes and claims the process for the dimerization of monoalkyl benzenes. For example, by adding 57.5 grams (1.03 moles) of isobutylene over a period of 90 minutes to 212 grams (2.01 moles) of ethylbenzene and 155 grams (7.75 moles) of hydrofluoric acid, the temperature being maintained at a minimum of 100 C., there was obtained 33 grams v(0.057 mole) of l-phenyl-l-pethylphenylethane, the dimer of ethylbenzene. In accordance with the process f the present invention, benzene is included in the reaction mixture preferably in at least an equal molar quantity with the ethylbenzene. In the presence of benzene, the formation of the dimer of ethylbenzene is suppressed and `instead there is formed the alkylation product of benzene and ethylbenzene, namely, 1,1-diphenylethane, the quantity formed being about the same as that obtained for the dimer `of ethylbenzene in Serial No. 381,752.

At the minimum temperature of 100 C., a small amount of the alkylation product of benzene and tertiary olefin maybe observed, while at higher temperatures, say about 125 C., substantially none of this productis obtained in the reaction.

The diarylalkane products of the present process can be used as lubricating oil additives, intermediates in the preparation of detergents, for the synthesis of other compounds, and the like.

When monoalkyl benzenes other than ethylbenzene and when mononuclear aromatics other than benzene are employed, substantially equivalent results are obtained. Also other oletins, as above described, may be substituted for isobutylene and equivalent results obtained.

The invention claimed is:

l. Process of alkylation which comprises reacting a mononuclear aromatic hydrocarbon having from 0 to `4 methyl groups attached to the aromatic nucleus with a monoalkyl benzene having the formula wherein R is a material selected from the group consisting of alkyl radicals having from l to 20 carbon atoms and cycloalkyl radicals having from 1 to 20 carbon atoms, and wherein R1 is a material selected from the group consisting of a hydrogen atom, alkyl radicals having from l to 20 carbon atoms and cycloalkyl radicals having from l to 20 carbon atoms in the presence of a tertiary olefin and hydrogen uoride, said reaction being performed in liquid phase at a temperature of from 100 C. to 185 C.

2. Process of alkylating benzene with a monoalkyl benzene having the formula 1 to 20 carbon atoms and cycloalkyl radicals having from l to 20 carbon atoms which comprises reacting in liquid phase at a temperature of from 100 C. to 185 C., benzene with said monoalkyl benzene in the presence of a tertiary olefin having from 4 to,7 carbon atoms and hydrogen uoride.

3. Process according to claim 2 wherein said monoalkyl benzene is ethylbenzene.

4. Process according to claim 2 wherein said monoalkyl benzene is cumene.

5. Process according to claim 2 wherein said monoalkyl benzene is n-propylbenzene.

6. Process according to claim 2 wherein said monoalkyl benzene is secondary butylbenzene.

7. Process according to claim 2 wherein said monoalkyl benzene is secondary amylbenzene.

8. Process for the preparation. of 1,1-diphenylethane which comprises contacting an admixture of benzene and ethylbenzene with a tertiary olelin and hydrogen iluoride, said contacting being performed in liquid phase at a temperature of 100 C. to 185 C. and separating 1,1-diphenylethane from the reaction mixture.

9. Process according to claim 8 wherein the tertiary olefin is added to an admixture of benzene, ethylbenzene,

and hydrogen iluoride.

10. Process according to claim 9 wherein the tertiary olefin is osobutylene.

11. Process of alkylating toluene with a monoalkyl benzene having the formula H i-R wherein R is a material selected from the group consisting of alkyl radicals having from 1 to 20 carbon atoms and cycloalkyl radicals having from 1 to 20 carbon atoms, and wherein R1 is a material selected from the group consisting of a hydrogen atom, alkyl radicals having from l to 20 carbon atoms and cycloalkyl radicals having from l to 20 carbon atoms which comprises reacting in liquid phase at a temperature of from C. to 185 C., toluene with said monoalkyl benzene in the presence of a tertiary olefin and hydrogen uoride.

References Cited in the file of this patent UNITED STATES PATENTS 2,671,815 Pines et al. Mar. 9, 1954 

1. PROCESS OF ALKYLATION WHICH COMPRISES REACTING A MONONUCLEAR AROMATIC HYDROCARBON HAVING FROM 0 TO 4 METHYL GROUPS ATTACHED TO THE AROMATIC NUCLEUS WITH A MONOALKYL BENZENE HAVING THE FORMULA 